(Hypertension. 1997;30:629.)
© 1997 American Heart Association, Inc.
Articles |
Lipid Metabolism Alterations in Normotensive Subjects With Positive Family History of Hypertension
From the Hypertension Unit, Heart Institute, HCFMUSP, São Paulo, Brazil.
Correspondence to Heno Ferreira Lopes, MD, Hypertension Unit, Heart Institute, Av Dr Eneas de Carvalho Aguiar, 44, 05403-000 São Paulo, Brazil.
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Abstract |
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Abstract Metabolic abnormalities are usually reported in hypertensive patients. These metabolic alterations seem to begin in childhood. The young offspring of hypertensive parents have not been studied thoroughly for metabolic alterations. The aim of this study was to examine the level of total cholesterol, LDL cholesterol, VLDL cholesterol, HDL cholesterol, uric acid, glycemia, aldosterone, and plasma renin activity in a population of 42 young, slender normotensive subjects with positive family history of hypertension (FH+) or negative family history of hypertension (FH-). Measurements were made in 20 young normotensive subjects (age 21.1±2.2 years, 11 males, 15 white, 5 oriental, body mass index of 22.1±2.3 kg/m2) with FH+ and 22 young normotensive subjects (age 19.9±1.4 years, 17 males, 17 white, 5 oriental, body mass index of 22.1±2.3 kg/m2) with FH-. The total cholesterol (4.47±0.8 versus 3.95±0.6 mmol/L), LDL cholesterol (2.74±0.63 versus 2.36±0.61 mmol/L), VLDL cholesterol (0.5±0.25 versus 0.35±0.09 mmol/L), and triglycerides (2.52±1.26 versus 1.76±0.5 mmol/L) were significantly elevated (P<.05) in the FH+ group compared with the FH- group. The total cholesterol/HDL cholesterol ratio was significantly higher in the group with a positive family history of hypertension (3.75±0.02 versus 3.11±0.02, P<.05). Glycemia was slightly elevated in the FH+ group (2.16±0.29 mmol/L) but was not significantly different from that of the FH- group (2±0.2 mmol/L). Uric acid, plasma renin activity, and aldosterone were similar in both groups. We conclude that young, slender normotensive subjects with a positive history of hypertension show alterations in lipid metabolism, suggesting a positive correlation between lipid metabolism and hypertension heredity.
Key Words: hypertension • blood pressure • lipid metabolism
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Introduction |
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Hypertension is frequently accompanied by metabolic disorders such as elevated triglyceride level, low level of HDL cholesterol, increase in LDL cholesterol, and glucose intolerance or insulin resistance.1 Borderline hypertensive subjects when compared with normotensive subjects have higher cholesterol level, higher triglyceride level, lower HDL cholesterol, and higher insulin level.2 DNA familial markers of some lipid abnormalities or hypertension have been described before.3 Lipid abnormalities and hypertension independently or occurring together are important risk factors to the atherosclerosis process, and this process seems to begin early in life, in childhood. Metabolic and endocrine abnormalities (elevated total cholesterol, LDL cholesterol, low HDL cholesterol, and elevated norepinephrine, renin, and insulin) have been observed more frequently in normotensive subjects with a family history of hypertension than in subjects with a negative family history of hypertension,4 5 6 resulting in a positive correlation between lipid metabolism and hypertension heredity. Most of the data involving metabolism and the genetics of hypertension were obtained in adult normotensive subjects and not in children and postpubertal subjects, when hypertension seems to begin. We have previously shown that postpubertal normotensives with a positive family history of hypertension have an elevated casual systolic blood pressure and elevated sustained (1-hour resting period, Finapres, Ohmeda-2300) systolic, mean, and diastolic resting blood pressures, suggesting a permanent abnormality rather than a momentary hyperreactivity producing the increased arterial pressure.7 The aim of this study was to evaluate the metabolic and humoral profile in young, slender normotensive subjects with positive and negative histories of hypertension.
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Methods |
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Subjects
Forty-two healthy normotensive medical students were selected for the study. They were considered normotensive when casual blood pressure measured after 10 minutes of rest in sitting position at least two times was <140/90 mm Hg. Arterial blood pressure was measured with a mercury sphygmomanometer, using the disappearance of Korotkoff sounds (phase V) as the criterion for the determination of diastolic blood pressure. Subjects with obesity were excluded; degree of obesity was estimated by determining body mass index. The parents with positive or negative history of hypertension were identified by finding evidence in their medical records of antihypertensive treatment or by direct measurement of parents’ blood pressure. No history of diabetes was detected in the parents. Subjects were subdivided into two groups according to their parents’ blood pressure status: positive family history (FH+) when one or two parents were hypertensive and negative family history (FH-) when both parents were normotensive. The age of the population was limited to 18 to 25 years. The characteristics of the two groups are presented in Table 1, showing that the two groups were similar in regard to age, sex, and race. All participants signed an informed consent approved by the Ethics Committee from the Hospital das Clinicas, São Paulo University.
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Protocol
All subjects reported to our laboratory at approximately
8 AM after an overnight fast. After the subjects
rested for 1 hour in a supine position, blood samples were
collected for measurement of total cholesterol, HDL
cholesterol, LDL cholesterol, VLDL
cholesterol, uric acid, triglycerides,
glycemia, plasma renin activity, and aldosterone. Total
cholesterol level was measured by the CHOD-PAP method
and the LDL-cholesterol concentration was calculated indirectly
(Friedewald formula). The HDL cholesterol was separated
with the phosphotungstic acid/magnesium chloride method. Glucose,
triglycerides, and uric acid were measured by the enzymatic
colorimetric test (GPO/PAP method).
Aldosterone and plasma renin activity were measured by
radioimmunoassay.
Statistical Analysis
Statistical analysis was performed with the statistical
software SAS/STAT.8 Comparisons between categorical
variables were performed with the 
2 test.
Student’s nonpaired t test was applied for the comparison
between two related samples. Values for continuous variables are
expressed as mean±SD. A value of P<.05 was the minimal
level of statistical significance.
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Results |
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Table 1 shows that the two groups of youngsters under study did not differ significantly regarding age, sex, race, and body mass index. The mean systolic and diastolic blood pressures were significantly higher in the FH+ than in the FH- group (Table 1). Table 2 shows that mean plasma total cholesterol, LDL cholesterol, VLDL cholesterol, and triglycerides were significantly higher in normotensive subjects with positive history of hypertension than in normotensive subjects without history of hypertension, whereas HDL cholesterol did not differ in either group. In addition, the ratio of total cholesterol to HDL cholesterol was significantly higher in the FH+ than in the FH- group. The uric acid level was similar in the FH+ (0.12±0.03 mmol/L) and FH- (0.12±0.03 mmol/L) groups, respectively. Mean fasting plasma glucose was slightly elevated in the FH+ group (2.16±0.29 mmol/L) but was not significantly different from that of the FH- group (2±0.2 mmol/L, P=NS). The plasma renin activity was not different in the FH+ and FH- groups (1.0±1.0 and 1.0±0.9 ng · mL-1 · h-1, respectively), and aldosterone levels did not differ between FH+ and FH- groups (0.27±0.07 and 0.24±0.09 mmol/L, respectively).
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Discussion |
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Metabolic abnormalities and hypertension are frequently associated, and this fact contributes to the development of cardiovascular disease. The metabolic abnormalities seem to develop along with hypertension early in life in subjects with genetic predisposition to hypertension. As we have observed before, young normotensive subjects with a positive family history of hypertension exhibit a sustained elevated blood pressure; they seem to reflect not just a transient blood pressure elevation, but one representing a premature and true increase in blood pressure levels.7 In the present study, the young, lean normotensive subjects with a positive history of hypertension had elevated levels of total cholesterol, LDL cholesterol, VLDL cholesterol, and triglycerides when compared with young, lean normotensives without a history of hypertension. The HDL cholesterol level was not different in the FH+ and FH- groups. The basal glucose was slightly elevated in the FH+ group, but it was not significantly different. These characteristics found in normotensive youngsters with a positive history of hypertension, associated with other abnormalities such as insulin resistance and altered glucose tolerance, are relatively frequent in hypertensive patients.6 9 Adult normotensive patients with a family history of hypertension compared with hypertensive patients with or without a family history of hypertension have a similar metabolic profile.6 Metabolic alterations in offspring of hypertensive subjects have been observed before,5 10 11 but the studies were usually performed in subjects older than in our population, and these subjects were exposed for longer times to environmental factors, which may interfere with the metabolic condition. The metabolic abnormalities observed in this study could possibly contribute to vascular structural and reactivity modification early in life. Lipid metabolism alterations are considered risk factors for coronary artery disease, and subjects with a positive history of hypertension could be more susceptible to hypertension and cardiovascular disease. Therefore, this population deserves special preventive care. Treatment of hypertension usually begins during adulthood, at a time when considerable damage may have already been done to the arterial system, the left ventricle, and perhaps to other organs.12 Consequently, it is convenient to identify individual children who are at high risk for cardiovascular disease, according to family history of hypertension, presence of obesity, inactivity, and consumption of high-fat meat. The plasma renin activity and aldosterone level were described as similar or low in offspring of hypertensive parents,13 14 and in our study the values did not differ between groups. Also, the uric acid level was similar in both groups. In conclusion, young, lean normotensive subjects with a positive history of hypertension show alterations in lipid metabolism, suggesting a positive correlation between lipid metabolism and hypertension heredity.
Received March 17, 1997; first decision April 30, 1997; accepted May 19, 1997.
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References |
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